Anjem Choudary, one of Britain’s most notorious hate preachers, has been convicted of supporting Islamic State. He now faces up to a decade in jail.

Choudary was convicted at the Old Bailey after jurors heard that he had sworn allegiance to the terrorist group, and urged his followers to do the same in a series of videos broadcast via YouTube.

Both Choudary and his co-defendant, Mohammed Rahman, 33, urged their supporters to obey Islamic State’s leader Abu Bakr al-Baghdadi and to travel to Syria to support Islamic State, also referred to as “the caliphate”, the court heard.

The pair were convicted in July but details of the court case, including the verdict, could not be reported until today. They both face up to ten years in jail for inviting support for a proscribed organisation, and will be sentenced in September.

Prosecutor Richard Whittam QC said: “The prosecution case is that whichever name is used, the evidence is quite clear: when these defendants were inviting support for an Islamic state or caliphate they were referring to the one declared in Syria and its environs by Ibrahim [Abu Bakr] al-Baghdadi at the end of June 2014.

“Terrorist organisations thrive and grow because people support them and that is what this case is about. Do not confuse that with the right of people to follow the religion of their choice or to proclaim support for a caliphate.”

As part of the evidence jurors were shown a YouTube video lasting one hour and six minutes, uploaded to Choudary’s YouTube channel on 9 September 2014, titled How Muslims Assess the Legitimacy of the Caliphate.

The video consisted of a speech by Choudary, played over the image of a map of northern Africa, the Middle East, north-west Asia and southern Europe.

Choudary begins by setting out his views about the requirements of a legitimate Islamic caliphate, then explains why he sees Islamic State as meeting the criteria, the Guardian has reported.

“The lesson from this narration is that obedience to the caliph is an obligation, if they rule by the sharia. And to obey them obviously means they must be established,” he said.

He added: “I would just say, uh you know, for people who want to live under sharia law, obviously this is a great thing, and for those people who say we are promoting Isis, they are not even called Isis any more. Rather, you have an Islamic state where you have millions of people who are governed by the sharia law and I don’t think it is against the law to go and live there and want to abide by sharia law.”

In another lecture dating from March 2013, which was presented to the jury as background evidence, Choudary makes clear his desire to see a Caliphate established, and his support for military action by an Islamic State.

He said: “That is why the kuffar [non-believers] are worried, my dear Muslims. When the Muslims of the subcontinent gather together. When the Talibaninshallah [God willing] and the mujahideen take Afghanistan and then declare jihad against the mourtad of Zardini and his army of tawaghit, and when they annex and take India and they take Bangladesh and they take Indonesia, you have over a billion Muslims in the area.

“We don’t have any borders, my dear Muslims. It is about time we resumed conquering for the sake of Allah.

“Next time when your child is at school and the teacher says ‘what do you want when you grow up, what is your ambition?’, they should say to dominate the whole world by Islam, including Britain, that is my ambition.”

Speaking to Sky News on the night before his conviction, the 49-year-old from east London said: “If you look at my speeches, I have said the same thing for 20 years. For me, it is a matter of worship.

“If people are implementing the Sharia, then I cannot shy away from what the divine text says in relationship to that.

“If you cannot say when you believe in something and you cannot share that view, then you don’t really have freedom to express yourself in this country.”

However, Whittam noted during his defence that Choudary and Rahman were both “acutely aware” of the potential for criminal charges over their support for Islamic State.

“The prosecution alleges that this led to great care in the way in which the defendants expressed themselves publicly, particularly after Isil was proscribed as a terrorist organisation by the home secretary,” he told the court.

Born in London, Choudary graduated from Guildford College of Law and set up his own solicitor’s firm in his 20s. However, he gave up the practice after deepening his Muslim faith, eventually going on to study sharia law under Syrian-born Bakri Muhammad, a Salafi Islamist militant leader who in the 1990s formed al-Muhajiroun with the aim of promoting sharia.

Choudary courted controversy, first with al-Muhajiroun, and later with Islam4UK, for which he was spokesman at the time the group released “incendiary statements” calling for Buckingham Palace to be turned into a mosque and Nelson’s Column to be destroyed.

He shot to prominence by holding a news conference to praise Osama bin Laden following the 9/11 attack, and did the same following London’s 7/7 bombing, the perpetrators of which he had links to through his organisations.

His conviction is the result of a two-year, multimillion-pound investigation by Scotland Yard designed to bring to a close his two decades of extremist preaching.